Custom fields menu items

I am trying to add custom fields to the menu items. I have found examples on using the following hook:

wp_nav_menu_item_custom_fields

For example on this site: https://pressidium.com/blog/adding-custom-fields-to-wordpress-menu-items/

As well as on the official WordPress release blog it is stated that it is as simple as doing something like this in the functions.php file to make something appear:

function my_menu_item_field() {
        echo 'A menu item test field';
    }
    add_action( 'wp_nav_menu_item_custom_fields', 'my_menu_item_field' );

I have tried all sorts of examples but nothing appears at all. I am using WordPress 6.3.2 where the menu section is in the customizer menu.